1. Field of the Invention
This invention relates generally to safety devices used to secure equipment in place and enable the performance of maintenance or other work on such equipment with safety. More particularly, the invention relates to lock down devices used to preclude movement of a loaded oil well pumping unit and thereby permit work on it to be performed safely.
2. Description of the Related Art
In industry, motor-driven machinery and other equipment frequently require securing in order to permit maintenance and/or modifications to be performed in complete safety, free from the concern that the equipment could move suddenly. Precautionary measures, such as the applying of brakes and the shutting off of engines or electrical power, are common means of increasing workplace safety. Such safeguards and practices occasionally fail or are overlooked, so multiple redundant systems are often used.
In the petroleum industry, a variety of methods are used for extracting oil from underground reservoirs. Perhaps one of the most common of these methods is an oil well pumping unit known as the "walking beam" type. With some imagination, these walking beam pumping units resemble giant grasshoppers, each one seesawing its giant pump arm up and down as it lifts oil from underground.
In the course of regular maintenance or modifications, a lift rod connected to the head of the pump arm must be disconnected. To perform this operation, the pump arm is operated through its up-down cycle until the pump arm brings the pump head down to its lowest position, closest to the ground. At this point the unit is stopped and a safety brake is applied.
In current practice, a chain is passed over the pump arm and secured to the platform or base of the pump unit. The addition of this secured chain provides an added degree of safety, should the safety brake mechanism fail. Such an arrangement is similar to that set forth in U.S. Pat. No. 4,525,914 issued to Bryan et al. The Bryan patent uses chain for securing the horsehead of an oil well pump, but does not provide the additional ease and safety afforded by the present invention.
The installation and securing of a chain over a pump arm requires rig personnel to climb up on the pump unit in order to manually pass the chain over the pump arm. As maintenance and repair operations are performed in the field, the rig personnel must scale the pump unit, frequently without safety gear or other fall protection devices, all the while at considerable distance from emergency medical care. Additionally, if the chains used for this purpose are not regularly inspected and tested, they may fail without warning. The failure of a chain may allow the pump arm to spring upward suddenly and cause substantial damage to the pump unit and other rig equipment, as well as seriously injure rig personnel. Commonly used walking beam pump units require rig personnel to scale the unit to heights of 20 to 30 feet in order to pass a safety chain over the pump arm. A slip or fall from such height could easily result in serious injury. U.S. Pat. No. 4,092,872 issued to McClure disclosed a safety attachment for an oil well horsehead utilizing jointed parallel straps. The McClure patent does not teach the lock down safety features of the present invention.
Several patents disclose clamping arrangements for attaching to a flanged beam. Examples of such clamping arrangements are taught in U.S. Pat. Nos. 2,877,974 of Estes, U.S. Pat. No. 3,084,893 of Ruth and U.S. Pat. No. 4,799,639 of Riley. However, none of these patents teaches or suggests the structural combination of the present invention.